1. Field of the Invention
The present invention relates to a method and device for use in a sewing machine and, more particularly to a method and device for creating non-ravel stitch data for a sewing machine.
2. Description of the Related Art
Generally, a sewing machine is provided with a stitch forming device including a mechanism for reciprocating a needle and also including a loop taker for forming stitches in cooperation with the needle. A sewing machine is further provided with a material moving device for moving a material to be sewn, e.g., a work fabric, in a direction perpendicular to a reciprocating direction of the needle. The sewing machine is designed to automatically form a stitch pattern on the material to be sewn, by controlling the material moving device according to stitch pattern data in synchronism with the reciprocation of the needle.
Meanwhile, it is known that non-ravel stitching for preventing fray of a seam end is performed at at least one of the start and the end of the stitch pattern. There is disclosed in Japanese Laid-open Patent No. 1-262891 (laid open on Oct. 19, 1989) a device for automatically creating non-ravel stitch data for performing the non-ravel stitching operation.
The sewing machine described in the above cited reference can automatically form a stitch pattern on a work fabric according to stitch pattern data. This sewing machine can also automatically perform processing of the stitch pattern data, so as to expand or contract the stitch pattern. Further, this sewing machine can automatically perform creation of the non-ravel stitch data, so as to perform the non-ravel stitching at the start and/or the end of the stitch pattern.
In the above conventional sewing machine, the non-ravel stitching is always performed at the start and/or the end of the stitch pattern. However, when a pitch of each stitch itself constituting the stitch pattern is small, there is no possibility of fray of the seam end, and it is therefore unnecessary to perform the non-ravel stitching. Particularly when the stitch pattern is contracted to markedly reduce the stitch pitch, undue non-ravel stitching makes the stitches of the stitch pattern appear bulbous, thus deteriorating the appearance of a sewn product.